The invention relates to a secondary air system for an internal combustion engine. It is known that to improve the oxidation of hydrocarbons and carbon monoxides so-called secondary air, that is, additional air, can be blown into the exhaust gas end of the internal combustion engine.
German Patent Application DE-A-42 19267 describes a system for blowing secondary air for internal combustion engines in which a compressor is driven by an air-flow machine acting as a motor. The air-flow machine is connected parallel to a duct section with a throttle, the duct section being disposed upstream from a throttle connection to increase the power. The aspirated air is guided by a switch valve either through the throttle or through the air-flow machine.
A disadvantage of the known system is that the aspirated air fed to the motor is reduced by the additional throttle. Also, an additional element exists in the aspirated air train which has to be regulated according to the load on the motor.
It is also known to use a diaphragm pump for the injection of secondary air into internal combustion engines. A disadvantage of this system is the need to provide a pressure reservoir, which thus makes the system less economical.